In the performance of electric discharge forming, the discharging gap, as the impulsive pressure source, is often bridged with a fine metal wire prior to occurrence of an impulse current. The quantity of energy released into the dischargingg gap in
CLR-Gap series circuit has a maximum if the voltage drop across the gap is approximately equal to the half of the starting voltage of capacitor. the gap of the length satisfying the condition above is usually too large to be breaked down without a fuse-wire. The principal effect of the fine metal wire may be striking of an arc in the gap. The energy poured into the wire to melt and vapourize it must, however, have the effect on the forming.
This paper reports experimental studies of the effect of the fusewire on the bulging in free-forming. Rectangular impulse currents were used to supply engery into the under-water discharging gap, and lead wire segments were used as fuses in the gap. Aluminium sheets were bulged in free-forming, and the hights of bulges were examined on basis of the previous discussion.
The bulging hight,
h, may be expressed as follows:
h2=
K{
kE(
Qa+Δ
Q00)-Δ
Q}
where,
K=
k1/(
k2+
Ta), Δ
Q=Δ
Q0+
kQTa,
Qa: amount of discharge in arc,
Ta: duration of arc,
Δ
Q00: apparent increase of amount of discharge in arc, which is caused by the energy poured into the wire segment.
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